[libc][math][C23] implementation of cospi #131018

ghost · 2025-03-12T19:56:53Z

initial draft of the implementation of cospi

github-actions · 2025-03-12T19:57:14Z

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llvmbot · 2025-03-12T19:57:48Z

@llvm/pr-subscribers-libc

Author: None (lara254)

Changes

initial draft of the implementation of cospi

Full diff: https://github.com/llvm/llvm-project/pull/131018.diff

11 Files Affected:

(modified) libc/config/darwin/arm/entrypoints.txt (+1)
(modified) libc/config/linux/aarch64/entrypoints.txt (+1)
(modified) libc/include/math.yaml (+6)
(modified) libc/src/math/CMakeLists.txt (+1)
(added) libc/src/math/cospi.h (+20)
(modified) libc/src/math/generic/CMakeLists.txt (+17-2)
(added) libc/src/math/generic/cospi.cpp (+91)
(modified) libc/test/src/math/CMakeLists.txt (+16)
(added) libc/test/src/math/cospi_test.cpp (+30)
(modified) libc/test/src/math/smoke/CMakeLists.txt (+12)
(added) libc/test/src/math/smoke/cospi_test.cpp (+48)

diff --git a/libc/config/darwin/arm/entrypoints.txt b/libc/config/darwin/arm/entrypoints.txt
index 7972d285f963a..f02aab5b65e31 100644
--- a/libc/config/darwin/arm/entrypoints.txt
+++ b/libc/config/darwin/arm/entrypoints.txt
@@ -139,6 +139,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.coshf
     libc.src.math.cos
     libc.src.math.cosf
+    libc.src.math.cospi
     libc.src.math.cospif
     libc.src.math.dfmal
     libc.src.math.dsqrtl
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 6c2be4d3b0b99..ff9f65f05774f 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -424,6 +424,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.cos
     libc.src.math.cosf
     libc.src.math.coshf
+    libc.src.math.cospi
     libc.src.math.cospif
     libc.src.math.daddl
     libc.src.math.ddivl
diff --git a/libc/include/math.yaml b/libc/include/math.yaml
index a66f981030864..4c6744ca18633 100644
--- a/libc/include/math.yaml
+++ b/libc/include/math.yaml
@@ -249,6 +249,12 @@ functions:
     arguments:
       - type: long double
       - type: long double
+  - name: cospi
+    standards:
+      - stdc
+    return_type: double
+    arguments:
+      - type: double
   - name: dmulf128
     standards:
       - llvm_libc_ext
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index f18a73d46f9aa..3623bb637d691 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -99,6 +99,7 @@ add_math_entrypoint_object(cosh)
 add_math_entrypoint_object(coshf)
 add_math_entrypoint_object(coshf16)
 
+add_math_entrypoint_object(cospi)
 add_math_entrypoint_object(cospif)
 add_math_entrypoint_object(cospif16)
 
diff --git a/libc/src/math/cospi.h b/libc/src/math/cospi.h
new file mode 100644
index 0000000000000..fc68b8d046267
--- /dev/null
+++ b/libc/src/math/cospi.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for cospi -------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_MATH_COSPI_H
+#define LLVM_LIBC_SRC_MATH_COSPI_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+double cospi(double x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_SINPIF_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 3114289bad486..38981bfd0eae7 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1,5 +1,3 @@
-
-
 add_entrypoint_object(
   canonicalize
   SRCS
@@ -381,6 +379,23 @@ add_entrypoint_object(
     libc.src.__support.macros.optimization
     libc.src.__support.macros.properties.types
 )
+add_entrypoint_object(
+  cospi
+  SRCS
+    cospi.cpp
+  HDRS
+    ../cospi.h
+  DEPENDS
+    .sincosf_utils
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.fma
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.macros.optimization
+    libc.src.__support.FPUtil.polyeval
+    libc.src.math.pow
+    libc.src.__support.FPUtil.basic_operations
+)
 
 add_entrypoint_object(
   cospif
diff --git a/libc/src/math/generic/cospi.cpp b/libc/src/math/generic/cospi.cpp
new file mode 100644
index 0000000000000..8c743b85a756a
--- /dev/null
+++ b/libc/src/math/generic/cospi.cpp
@@ -0,0 +1,91 @@
+//===-- double-precision cospi function ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/cospi.h"
+#include "sincos_eval.h"
+#include "src/__support/FPUtil/BasicOperations.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/double_double.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+#include "src/math/fmul.h"
+#include "src/math/generic/sincosf_utils.h"
+#include "src/math/pow.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+static LIBC_INLINE void sincospi_poly_eval(double k, double y, double &sin_k,
+                                           double &cos_k, double &sin_y,
+
+                                           double &cosm1_y) {
+
+  // Q3 = fpminimax(sin(x*pi), 7, [|64...|], [-0.0078125, 0.0078125]);
+  sin_k =
+      k * fputil::polyeval(k, 0x1.59b6a771a45cbab8p-94, 0x1.921fb54442d1846ap1,
+                           -0x1.8633470ba8bd806cp-76, -0x1.4abbce625be56346p2,
+                           0x1.d3e01dfd72e97a92p-61, 0x1.466bc67713dbbfp1,
+                           -0x1.14c2648595e2ad4p-47, -0x1.32d1cc20b89301fcp-1);
+
+  sin_y =
+      y * fputil::polyeval(k, 0x1.59b6a771a45cbab8p-94, 0x1.921fb54442d1846ap1,
+                           -0x1.8633470ba8bd806cp-76, -0x1.4abbce625be56346p2,
+                           0x1.d3e01dfd72e97a92p-61, 0x1.466bc67713dbbfp1,
+                           -0x1.14c2648595e2ad4p-47, -0x1.32d1cc20b89301fcp-1);
+
+  // Q1 = fpminimax(cos(x * pi), 7, [|64...|], [-0.0078125, 0.0078125]);
+  cos_k =
+      k * fputil::polyeval(k, 0x1p0, 0x1.a5b22c564ee1d862p-84,
+                           -0x1.3bd3cc9be45d30e6p2, -0x1.5c2328fefbe60d3ep-66,
+                           0x1.03c1f080a6907a6p2, 0x1.569a4d5c5018eecap-51,
+                           -0x1.55d1f72455a9848ap0, -0x1.6b18e5f7fc6c39a6p-38);
+
+  cosm1_y =
+      y * fputil::polyeval(y, 0x1p0, 0x1.a5b22c564ee1d862p-84,
+                           -0x1.3bd3cc9be45d30e6p2, -0x1.5c2328fefbe60d3ep-66,
+                           0x1.03c1f080a6907a6p2, 0x1.569a4d5c5018eecap-51,
+                           -0x1.55d1f72455a9848ap0, -0x1.6b18e5f7fc6c39a6p-38);
+}
+
+LLVM_LIBC_FUNCTION(double, cospi, (double x)) {
+  using FPBits = typename fputil::FPBits<double>;
+  FPBits xbits(x);
+
+  double x_abs = fputil::abs(x);
+  double p = 0x1p52; // 2^p where p is the precision
+
+  if (LIBC_UNLIKELY(x_abs == 0U))
+    return x;
+
+  if (x_abs >= p) {
+    if (xbits.is_nan())
+      return x;
+    if (xbits.is_inf()) {
+      fputil::set_errno_if_required(EDOM);
+      fputil::raise_except_if_required(FE_INVALID);
+      return FPBits::quiet_nan().get_val();
+    }
+    return FPBits::zero(xbits.sign()).get_val();
+  }
+  double n = pow(2, -52);
+  double k = fputil::nearest_integer(x * n);
+  double y = x - k;
+  double sin_k, cos_k, sin_y, cosm1_y;
+
+  sincospi_poly_eval(k, y, sin_k, cos_k, sin_y, cosm1_y);
+
+  if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0))
+    return FPBits::zero(xbits.sign()).get_val();
+
+  return fputil::cast<double>(fputil::multiply_add(
+      cos_k, cosm1_y, fputil::multiply_add(-sin_k, sin_y, cos_k)));
+}
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 53ddd301900c0..155178a0eb50f 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -39,6 +39,22 @@ add_fp_unittest(
     libc.src.math.cosf16
 )
 
+add_fp_unittest(
+  cospi_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    cospi_test.cpp
+  HDRS
+    sdcomp26094.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.cospi
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits
+)
+
 add_fp_unittest(
   cospif_test
   NEED_MPFR
diff --git a/libc/test/src/math/cospi_test.cpp b/libc/test/src/math/cospi_test.cpp
new file mode 100644
index 0000000000000..ff31bea42c742
--- /dev/null
+++ b/libc/test/src/math/cospi_test.cpp
@@ -0,0 +1,30 @@
+//===-- Exhaustive test for cospi -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===---------------------------------------------------------------------===//
+
+#include "src/math/cospi.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+#include <iostream>
+
+using LlvmLibcCospiTest = LIBC_NAMESPACE::testing::FPTest<double>;
+using namespace std;
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+static constexpr double POS_START = 0;
+static constexpr double POS_STOP = 200;
+
+TEST_F(LlvmLibcCospiTest, PositiveRange) {
+  for (double v = POS_START; v <= POS_STOP; ++v) {
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Cospi, v,
+                                   LIBC_NAMESPACE::cospi(v), 0.5);
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Cospi, -v,
+                                   LIBC_NAMESPACE::cospi(-v), 0.5);
+  }
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 6f94440d826d9..5fc99cb45f9a1 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -23,6 +23,18 @@ add_fp_unittest(
     libc.src.math.cosf16
 )
 
+add_fp_unittest(
+  cospi_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    cospi_test.cpp
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.cospi
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits
+)
 add_fp_unittest(
   cospif_test
   SUITE
diff --git a/libc/test/src/math/smoke/cospi_test.cpp b/libc/test/src/math/smoke/cospi_test.cpp
new file mode 100644
index 0000000000000..9c1feff995a26
--- /dev/null
+++ b/libc/test/src/math/smoke/cospi_test.cpp
@@ -0,0 +1,48 @@
+//===-- Unittests for cospi -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/FPUtil/cast.h"
+#include "src/errno/libc_errno.h"
+#include "src/math/cospi.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcCospiTest = LIBC_NAMESPACE::testing::FPTest<double>;
+
+TEST_F(LlvmLibcCospiTest, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::cospi(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::cospi(zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::cospi(neg_zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::cospi(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::cospi(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
+
+TEST_F(LlvmLibcCospiTest, Integers) {
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::cospi(-0x1.0000000000003p52));
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::cospi(-0x1.0000000000005p52));
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::cospi(-0x1.0000000000006p52));
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::cospi(0x1.0000000000003p52));
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::cospi(0x1.0000000000005p52));
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::cospi(0x1.0000000000006p52));
+}

add initial draft

a56711d

llvmbot added the libc label Mar 12, 2025

ghost marked this pull request as draft March 12, 2025 20:05

make the smoke tests pass

7ea78c4

ghost closed this Apr 2, 2025

ghost reopened this Apr 2, 2025

ghost closed this by deleting the head repository Apr 8, 2025

This pull request was closed.

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[libc][math][C23] implementation of cospi #131018

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